This invention relates to novel sulfonated diphenyldiisocyanates. In a further aspect, this invention relates to novel gels produced from the sulfonated diphenyldiisocyanates upon their addition to water. These novel gels are stable under acidic conditions and at elevated temperatures.
It is known that sulfonation of various aromatic mono- and poly-isocyanates yields compounds containing both isocyanate and sulfonic acid functionalities on one molecule wherein the sulfo group exclusively enters at the ortho position to the isocyanate group on the aromatic ring. This position is favored due to the formation of a six-membered heterocyclic ring by the ortho sulfonic acid group with the isocyanate group, referred to as a cyclic carbamic acid-sulfonic acid anhydride. See Angew. Chem. Int. Ed. Eng. 21, No. 11 (1982), pgs. 867-868.
U.S. Pat. No. 4,176,118 issued Nov. 27, 1979 to M. Petinaux et al. describes the partial sulfonation of 4,4'-diphenyl diisocyanates which yields exclusively tetranuclear uretdione diisocyanate disulfonic acids. The reaction is carried out employing molar ratios in the range of from about 1:1 to about 1:1.4 of diisocyanate to SO.sub.3 reagent, however it is disclosed that larger amounts of SO.sub.3 may be used without substantially altering the course of the reaction. The compositions of Petinaux et al. are described as being useful as crosslinking agents as well as useful in the polymer synthesis of, for example, polyisocyanurates, polycarbodiimides, polyimides, and polyurethanes.
Neither of the above references disclose or suggest the novel compositions of the present invention or the unique gel forming ability they possess upon addition to water.